Electric motor.



0. H. PIEPER. ELECTRIC MOTOR.

APPLICATION FILED 00T.26, 1905. RENEWED NOV. 22, 1912.

Patented Jan. 14, 1913.

- ternating current means which will enable OSCAR H. PIEPER, OF ROCHESTER. NEW'YORKL ELECTRIC Moron.

To all uriumv, 2'2. may concern: Be it known that I, OSCAR H. PIEPER, of Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Electric Motors; and I do hereby declare the following to be a full, clear, and exact description of the same, reference being bad to the accompanying drawings, forming a part of this specification, and to the reference-numerals marked thereon.

My, present invention relates to alternat ing current motors of the type in which the field and the armature are arranged in series and it has for its object to provide a method of construction whereby such a motor may be designed to operate at a constant prcde'tern'iincd speed when a load, and'as a further object to provide the speed of an alteri'iating current motor tioned to be increased or running" free.

To these and other ends the invention consist; in certain improvements and combinations of parts, -l-l as will be hereinafter more fully explained, the novel features being pointed out in the claims at the end of the specification.

In the drawingsr-the accompanying illustration is. a diagrammatic view of a motor constructed in accordance with my invention.

Similar reference numerals in the speci fication and drawing designate similar parts. 1

In illustrating my invention I have shown it applied to a motor embodying a field mag-- net 1 having pole pieces 2 and an armature 3 provided with a commutator 4 with which the brushes fo -and 6 cooperate. The armature windings 7 connected to the several commutator segments may be arranged as usual or in any preferred form.

One terminal of the field coils or windings B on the field magnet is connected to a line cauductor 9, while the other terminal 11 of the field coilor coils is connected to the brush 5 and the line conductor 10 leads to the brush 6, thus placing the field winding and the armature winding in series. An almotor of the above described type when operated without a load has a tendency for its armature to race or decreased when attain an excessively high speed due to the I gradually increasing counter electrornotli'c i tion of the Specification of Letters Patent. Application filed October 26, 1905, Serial No. 28f1,419. Renewed November running without of the type menthe counter ill. F.

Patented Jan. 14, 1913.

22, 1912. Serial No. 732,960.

force and consequently decreasing the field magnetism. In order to maintain a substantially constant field come this fault of racing I provide a field magnet with an inductive winding 12, separate from either the field winding 8 or the arn'iature winding 7 and providing in efect a secondary winding with the main field winding 8 as a primary. A field magnet in a motor of this type with both primary and secondary windings has a substantially constant field flux due to the con; trol of the current or energy in the primary circuit by the inductive or transformer action in the secondary circuit. Such a construction will permit the attainment of any primary and secondary windings.

In order to provide means fo' regulating the speedof the motor a variable winding, eitherinductive or non-inductive, is interposed in the secondary circuit by connecting the terminal 13 thereof to coils 14: and joiniiig the other terminal 15 to a movable switch arm 16 adapted to cooperate with a plurality of contacts 17 connected by wires 18 to various points on the coils 14.

By increasing the inductance of the motor circuit through the medium of the inductive auxiliary or secondary circuit, the phase-- lag of the current behind the impressed E. M. F. in the primary circuit is increased. The inductive action between the primary or main field coils and the secondary coils is similar to that of a transformer of the constant current type.

It is known that when the reactance of an alternating current circuit is large compared with the resistance, that the current does not vary greatly with changes of resistance. Moreover, it is also well known that the phase angle of in the circuit of a series alternating current. motor is reduced by the effect of the counter E. M. F. of the armature which is in phase with the current, and therefore increases the power factor or offestive hi. F.

it will be apparent that by increasing the rcactance of the motor circuit and consequently the phase-.ag of the current, the latter will remain substantially,constant and consequently t strength will also be maintained sul ly constant and will not be materially altered an increase of generated by the rotaarmature. For this reason the magnetism and over-- desired speed by suitable proportioning the r 25 magnet and the field and armature windings speed of the armature cannot.- increase over a certain predetermined amount, which can be varied by cutting in mor or less of the coils 14. I have thus provided an eit'ective 5 means of controlling the armature speed of series alternating current motors and preventing racing at no load.

A motor embodying the invention is particularly adapted for dental operations in 1 which the work performed varies greatly requiring a inotor susceptible of: instant speed changes when running tree, Without a load, other than the friction of the operating parts in their bearings.

I'claim as my invention: 7 1. In an alternating current motor of the Lcommutator type, the combination with the field magnet and field and armature wind ings arranged in series, of a highly inductive closed circuit winding on the field magnet arranged in inductive relation to the field windings only.

2. In an alternating current motor of the class described,""the combination with a field arranged in series, a secondary Winding on the field magnet arranged in a closed cir cult and in ITlClUCLlVG relation to the field,

Winding so that the induced current in said copie s 'thispatent. may lie (Rita-111E? for five cents secondary winding is produced only by cur rent in the main field Winding, and an auxiliary reactance coil in said closed circuit.

8, In. an alternating current motor of the 01215:?) described, the combination with the field magnetand the field and armature windings arranged in series, of an inductive winding arranged in a closed circuit on the field. the induced current in said "winding lacing produced only by current in the field a winding and serving to maintain. a constant magnetic strength in the field magnet, and

an auxiliary adjustable reactance coil in said closed circuit. 4-. In an alternating current motor, the

and field andarniat-ure windings arranged inseries, ofan inductive Winding on the field and arranged in a closed. circuit having no 'elec trical conmiaction with the field or armature windings, whereby the induced current/in combination With a field ina -et.

said Windingis produced only by current inand an auxiliary :1(l]11St the field winding, able inductive Winding interposed.in-said closed circuit. A @StlAR H. PIEPER.

Witnesses G. WILLARD R1035, W LTER l3. 'PAYNE.

each, by addressing the G'oinmissioner of Patents.

Washington, D. G2.

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